January: USAF F-22 Raptor grounded due to suspected toxins

The report cited "suspected contamination problems associated with the aircraft environmental control system and associated onboard oxygen generation system (OBOGS)" as the reason for the grounding, triggered by a crash in January 2011 that barred the aircraft from flying higher than 25,000ft.

February: Japan may halt F-35 purchase over price rise

In a letter addressed to the Pentagon, Japanese Defence Ministry bureau of finance and equipment chief Hideshi Tokuchi said: "I do hope that you share the view that a price increase is not an option for us."

Japan had originally planned to procure four F-35 jets in April 2012, with each aircraft set to cost between $111.1m and £123.6m.

However the US defense budget for 2013 placed the price of the aircraft for the US military at approximately $153m.

April: USAF fails to determine cause of F-22 Raptor pilot episodes

Pilots reported hypoxia-like symptoms while flying the aircraft, but a seven-month study of the F-22's onboard oxygen generation symptoms did not yield any significant reason why, with ten of 14 incidents remaining unexplained.

In other news, the UK Royal Air Force's first F-35 completed its inaugural flight from Lockheed Martin's Fort Worth facility, marking progress towards a series of checkout flights prior to being accepted by the UK MoD.

May: US military aircraft feature counterfeit Chinese parts

Counterfeit Chinese electronic parts were revealed to have been used in the construction of US military equipment, a Senate Armed Services Committee report revealed.

Prime Minister David Cameron had intended to switch from the F-35B to F-35C to be used aboard the nation's aircraft carriers, but spiraling costs and delays forced the decision to be reverted. The U-turn is estimated to have cost the UK £100m.

Russian news agency RIA quoted deputy director of the Russian service for military co-operation Vyacheslav Dzirkaln as saying "while the situation in Syria is unstable, there will be no new deliveries of arms there."

August: Iran to withdraw $4bn claim if Russia honours S-300 contract

Having issued a $4bn lawsuit to Russia, Iranian ambassador to Russia Mahmoud-Reza Sajjadi announced that the country would withdraw it should Russia honour its original S-300 SAM system delivery contract, signed in 2007.

Russia was forced to cancel the lucrative deal after it was found to breach a UN Security Council arms embargo forced on Iran in June 2010, despite Iranian claims to the contrary.

In other news, the USAF's test of the Boeing-built X-51A Waverider aircraft ended in failure, raising further questions about the future of the programme.

Despite hoping to reach hypersonic speeds, the USAF has just one hypersonic test aircraft remaining and doubts have been expressed regarding the feasibility of the technology.

September: Sukhoi conducts Su-30SM jet's maiden test flight

The test flight lasted for two hours and the super-manoeuvrable, thrust-vectoring aircraft was said to have performed flawlessly.

A total of 30 fighters have been ordered by the Russian Defence Ministry in a $3.3bn deal signed in March 2012.

October: Lockheed to upgrade Taiwan's F-16 fighter jets

In something of a surprise move, the US Government tasked Lockheed Martin with upgrading 145 F-16 fighter jets that belong to the Republic of China Air Force.

The $1.85bn contract will see Lockheed install AESA radars while also upgrading the aircraft's electronic warfare and avionics systems.

The USAF also moved to confirm that it would press ahead with the X-51A Waverider programme, with Air Force Research Laboratory programme manager Charlie Brink informing Reuters that the launch of the final X-51A test vehicle would go ahead in spring or early summer 2013, after modifications had been made.